Glow plug arrangement for internal combustion engines, especially for starting of diesel engines



1968 MINORUNAGAI ETAL 3,

GLOW PLUG ARRANGEMENT FOR lNTERNAL COMBUSTION ENGINES, ESPECIALLY FOR STARTING OF DIESEL ENGINES Filed Oct. 12, 1966 z I I v A .I I

United States Patent 3,407,794 GLOW PLUG ARRANGEMENT FOR INTERNAL COMBUSTION ENGINES, ESPECIALLY FOR STARTING OF DIESEL ENGINES Minoru Nagai, Kariya-shi, and Makoto Yato, Toyoda-shi, Japan, assignors to Nippon Denso Company Ltd., Kariya-shi, Japan Filed Oct. 12, 1966, Ser. No. 586,184 Claims priority, application Japan, Oct. 21, 1965, 40/ 64,658 7 Claims. (Cl. 123-145) ABSTRACT OF THE DISCLOSURE A glow plug arrangement for internal combustion engines in which a stream of fuel is guided through an annular gap about the rear portion of a heated glow plug having an outer metal shell and a wire helix embedded in insulating material in the shell so that when the glow plug is energized the fuel will be heated and completely evaporated in the annular gap without coming in contact with the wire helix and the fuel air mixture forming in the region of the front end of the glow plug be ignited by the latter.

The present invention relates to a glow plug arrangement for internal combustion engines, especially for starting of diesel engines in which a glow plug, having an outer shell and a wire helix insulated embedded therein with one end of the wire connected to the shell and the other end connected to a source of electrical current, projects into the suction conduit of the internal combustron engine.

Arrangements of this type are known which serve to facilitate starting of diesel engines, especially during the cold season, in which the fuel is heated and evaporated before it comes in contact with the glow plug and in which the fuel after being mixed with air in the suction conduit of the internal combustion engine is ignited by the heated glow plug. Other arrangements are known in which the fuel is atomized by an injection nozzle, mixed with air in the suction conduit and ignited by an electrical spark. Arrangements are also known in which the fuel is intermittently evaporated and ignited by means of a glow plug having an outer electrically heated wire helix.

All of these aforementioned arrangements known in the art have certain disadvantages. This first mentioned arrangement requires additional complicated devices for heating and evaporating the fuel before it comes into contact with the glow plug, and the injection nozzles used in the second mentioned arrangement for atomizing the fuel are frequently clogged by soot and other residues. Likewise the intermittent evaporation and ignition of the fuel by glow plugs with exposed wire helix does not provide for a satisfactory arrangement, since a complete evaporation of the fuel cannot be obtained therewith so that a reduced efficiency will result therefrom.

It is an object of the present invention to provide for a glow plug arrangement in which the above mentioned disadvantages are avoided.

It is a further object of the present invention to provide for a glow plug arrangement of simple construction by means of which the fuel is first heated, then completely evaporated and by means of which the fuel air mixture is finally ignited.

With these objects in view, the glow plug arrangement for internal combustion engines, especially diesel engines, mainly comprises a glow plug, wall means forming an annular gap about part of said glow plug and supporting the latter with a front portion of the glow plug projecting beyond the wall means, passage means communicating 3,407,794 Patented Oct. 29, 1968 in the region of a rear end of the annular gap with the latter for feeding liquid fuel into the annular gap, and means for connecting the rear end of the glow plug to a source of electrical energy for heating the glow plug, whereby fuel fed into the gap will be heated and evaporated therein and the fuel-air mixture forming in the region of the front end of the glow plug be ignited by the latter. In a preferred arrangment, the aforementioned annular gap is in part formed by a front portion of a stepped bore in a housing in which a rear portion of the glow plug is located and in part formed by a heat resistant metal tube surrounding the portion of the glow plug projecting from the housing and radially spaced from the outer surface of the glow plug. The front end of the glow plug preferably projects beyond the front end of the aforementioned metal tube.

The novel features which are considered as characteristic for the invention are set forth in particular in the appended claims. The invention itself, however, both as to its construction and its method of operation, together with additional objects and advantages thereof, will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, in which:

FIG. 1 is a partial cross sectional view of the glow plug arrangement according to the present invention; and

FIG. 2 is a partial cross sectional view of the front portion of the glow plug and the metal tube surrounding the same.

Referring now to the drawing, and more specifically to FIG. 1, it will be seen that the glow plug arrangement according to the present invention comprises a metal housing 1 formed with a stepped bore 1 extending in longitudinal direction therethrough in which a glow plug 3 is located, the enlarged rear end of which is pressed by means of a screw nipple 2 against the corresponding shoulder of the stepped bore 1. The front portion of the bore 1, that is the right portion thereof, as viewed in FIG. 1, has a diameter slightly larger than that of the outer diameter of the glow plug 3 so as to form an annular gap 11 about the glow plug, A passage 12 communicates with the annular gap 11 in the region of the rear end of the latter, which passage serves to feed liquid fuel from a source of liquid fuel, not shown in the drawing, into the annular gap 11. The annular gap 11 is extended beyond the housing 1 by a tube 4 of heat resistant metal which projects from the front face, that is the right face, as viewed in FIG. 1, of the housing 1 substantially coaxially with the glow plug 3. The tube 4 has preferably at its left end, as viewed in FIG. 1, a flange 4 formed with a central cylindrical cavity into which a corresponding cylindrical projection of the housing projects so that the tube 4 is properly centered with regard to the bore 1 in the housing and properly held on the latter. The inner diameter of the tube 4 is substantially equal to the diameter of the enlarged portion of the stepped bore 1', and the front portion of the glow plug 3 preferably projects beyond the free end of the metal tube 4. The metal tube 4 and the front end of the glow plug 3 are surrounded by a shielding tube 10 which is formed in the wall thereof with a plurality of openings 10' permitting passage of air in the suction conduit of the diesel engine into the interior of the shielding tube.

As best shown in FIG. 2, the glow plug 3 includes an outer metal shell 7 and a wire helix 6 located in the outer shell 7 embedded in insulating material 5, for instance ceramic powder. The front end of the wire helix 6 is welded to the front end, that is the right end as viewed in FIG. 2, of the outer shell 7, whereas the rear end of the helix 6, not shown in FIG. 2, is connected to a terminal electrode 8 extending through the screw nipple 2 insulateidtherefrom by-awing-943i.insulatingmaterial..

The electrode 8 is connected in a known manner, not shown in the drawing, to a-source of electrical energy so that current may flow from the electrodes throughthe wire helix 6 the. outer shell 7 of the, plug .3 which through the-housing l is connected to ground. Y.

;The above-described arrangement will operate as follows. If electrical current is supplied tothe electrode-'8, the current flowing through the wire helix 6', will heat the outer shell 7 of the glow plug .to red heat. If liquid fuel is now sent. through the passage '12 into .the annular gap 11, then the fuel passing through the annular gap will be heatedtherein and in the region of the metal tube 4 be evaporated. The evaporated fuel discharging at -the free end of the metal tube.4 is mixed with-air passing through the openings 10 of the shielding tube 10 and the thus form'ed mixture will be ignited at the glowing end of the glow plug projecting beyond the free end of the metal tube 4. Thethusformed flame is sucked together with the air heated thereby during actuation" of the starting motor into the cylinders of the diesel engine. The fuel injected during the compression stroke, shortly before the compression point into the cylinders of the diesel engine forms then with the air heated by the flame a hot gasmixture which ignites itself and thus facilitates starting of the diesel engine.

It will be understood that each of the elements described above, or two or more together, may also find a useful application in other types of glow plug arrangements for internal combustion engines differing from the types described above. 7

While the invention has been illustrated and described as embodied in a glow plug arrangement for facilitating start of a diesel engine, it is not intended to be limited to the details shown, since various modifications and structural changes may 'be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can by applying current knowledge readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention and, therefore, such adaptations should and are intended to-be comprehended within the meaning and range of equivalence of the following claims.

What is claimed as new and desired to be secured by Letters Patent is:

l. A glow plug arrangement for internal combustion engines comprising, in combination, a glow plug comprising an outer metal shell and a wire helix located in said shell and being embedded in insulating material,

said wire helix having a front end connected to saidshell and a rear end; wall means forming an annular gap about part of said outer shell of said glow plug and supporting the latter with a front portion of said glow plug projecting beyond .sai-d .wall means; passage. means communicating with "saidannular gap in thejregion of the rear end of the latter for v"feeding liquid fuel in said annular gap;,and means forconnecting said rear .end of said wire helix to a source of electric energyfor heating said glow plug, whereby fuel fed into said gap will flowin an. annular stream about the heated shell of the glow plugto be thus 'heated" and completely evaporated without coming in contact with said wire helixand so that the air fuel mixture forming in the regionof -the'front end of the glow plug will be ignited by the latter. v

2. A glow plug arrangement as defined in claim 1, wherein said wall meanscomprises a housing formed with a stepped b re therethrough,inwhichpart of said glow plug is .located projectingwith a front portion thereof beyond said housing, said stepped bore having a rear p'o'rtionof a diameter substantially equal to that of said glow plug and a front portion of a larger diameter so as to' form at least part of said annular gap between the large diameter surface of said bore and the outer surface of S s o p v e 3 A glow plug arrangement as defined in claim 2, wherein said wall means include further a tube of heatresistant metal projecting from said housing substantially coaxial with said glow plug and surrounding at least part of the front portion thereof radially spaced therefrom.

4; A glow plug arrangement asdefined in claim 3, wherein the inner diameter of said tube is substantially equal to said large diameter of said stepped bore.

5. A glow plug arrangement as defined in claim 3, wherein said glow plug projects beyond said metal tube.

6. A glow plug arrangement as defined in claimS, .and including a shielding tube surrounding said metal tube and said front portion of the glow plug, said shielding tube being formed in the wall thereof with openings therethrough permitting passage of combustion air through said openings into the interior of said shielding tube.

7. A glow plug arrangement as defined in claim 6, wherein said shielding tub'e extends slightly beyond the front end of said glow tube.

References Cited UNITED STATES lPATENTS 3,164,748 1/1965 Testerini 31798 3,353,520 1.1/ 1967 ,Haag.

LAURENCE M. GOODR'IDGE, Primary Examiner. 

